The residue from the wet extraction of zinc contains silver mainly as Ag.sub.2 S.
From Metallurgical Transactions B, Vol. 19 B, October 1988-803, it is known that the residues from the neutral wet extraction of zinc which are obtained by Mitsubishi Akita can be subjected to a flotation with AC-404 at a pH from 3.5 to 4.0 to recover 80% of the originally present silver and some gold.
It is also known from that publication that Zhuzhou recovers about 70% of the originally present silver by a flotation under acid conditions with the aid of a collector, which has not been specified.
That publication indicates further that Vieille Montagne has recovered about 90% of the originally present silver and about 75% of the originally present lead in two flotation concentrates by a flotation from residues from the acid wet extraction.
The wet extraction of zinc is usually performed in one or two wet extraction stages. The neutral wet extraction of zinc is usually performed at a slightly acid pH. In many cases the second extraction stage is omitted as uneconomical.